CDT Indexer behaving randomly (and almost never how it should)

[M-Marvin]

Hi, I did do a quick search about this problem here in the discussion and did see a few threads about similar problems, but I think my case might be s bit special, so I created this new thread anyway.

Basically, since I started using CDT for C++ development, I always noticed that the indexer behave ... strange sometimes.
It sometimes picks random functions und just always says that it can not find/resolve them, even tough if I click on it with Ctrl+Left-Click it jumps to the header defining it just fine.
Sometimes it also just generally marks everything as unresolved that comes from externally included headers for no reason (the header are still there, and I can open them fine using the Ctrl-Click method).
It changes between these behaviors mostly between IDE restarts, but sometimes it also just suddenly starts complaining about stuff, without doing more then en index rebuild or project refresh.

I now recently developed my own build system for java and c++ projects, and also made an Eclipse Plugin for it.
It just pushes a list of includes (headers) onto the CDT class path, which works perfectly fine, everything is recognized by the IDE and I can use autocomplete and open included headers.
But the indexer ... well ... it just got worse.

Its basically unusable right now, there are some rare times when it only complains about some of its "favorite functions" (the functions it always complained about, mostly memset, memfree and some std::chrono stuff)

I did reinstall eclipse a few times since I had this problem (aka since the first time using CDT).
Mostly during updates to newer versions.

I am currently on Eclipse 2024-12 4.34.0 and CDT 11.6, and it never changed during all those update times.
Maybe someone here can tell me if this is just a known issue with CDT or if there might be something wrong with my installation.
I cant think of any more things to try to fix this.

Using different toolchains does not change much by the way, no matter if I compile for linux, windows using mingw or SysGCC, its always the same.

[jonahgraham]

@M-Marvin I don't have an immediate solution (sadly) - but have a look at https://github.com/eclipse-cdt/cdt/blob/main/FAQ/Indexer.md and see if that helps progress things.

[M-Marvin]

Well, except the "Include Browser" this article gave me not much new information.
In the logs it says

!ENTRY org.eclipse.cdt.core 1 0 2025-06-24 12:36:34.348
!MESSAGE Indexed 'SerialPortAccess' (3 sources, 420 headers) in 5,74 sec: 71.004 declarations; 113.516 references; 0 unresolved inclusions; 1.184 syntax errors; 1.485 unresolved names (0,8 %)

But I still am missing like 80% of my symbols.
I did notice however that all of the missing symbols are from the toolchains include directories.
Meaning the std lib files, platform specific files such as windows.h or termios.h are always indexed without problems.

And example for an missing symbol even tough it is in the include browser is void __cdecl setbuf(FILE * __restrict__ _File,char * __restrict__ _Buffer) __MINGW_ATTRIB_DEPRECATED_SEC_WARN;

Maybe it has something to do with unsupported C++ features ?
I am not sure on which C++ version my toolchain exactly is, I use different ones, and all are affected.

[jonahgraham]

The message shows 0 unresolved inclusions and <1% unresolved names.

It could be that it is C++ version. Also sometimes some special macros are not well handled causing large amounts to be badly processed, for example __MINGW_ATTRIB_DEPRECATED_SEC_WARN maybe badly handled causing the declaration to be incorrectly parsed.

[M-Marvin]

Well, its just that it affects all my toolchains, not just mingw, also the linux ones.
I don't think any of these on an especially recent C++ version, I use some of them for 2 years now I think.

[M-Marvin]

Today I startet the same workspace with the same projects as yesterday.
In two out of four projects the indexer suddenly worked without problems, well, except its "favorite functions" again.
I did not change anything, not even an indexer rebuild, it just removed all errors and knew about every single symbol right from the start of the IDE.

Is there maybe some cache folder which could be messed up ?
I don't know what could cause it to change behavior so randomly ...